1. Field of the Invention
The invention relates generally to the field of electronic circuits, and more particularly to analog nonvolatile storage.
2. Description of Related Art
Analog storage devices provide an attractive alternative to storing electronic information in analog form rather than in digital form. The use of electrically erasable programmable read only memory (EEPROM) cells in an analog storage device avoid the necessity to convert an analog waveform to digital representation, reducing the complexity embodied in an integrated circuit as well as decreasing the die dimension. For additional background information on analog storage for voice recording and playback in EEPROM, the reader is referred to “A Non-Volatile Analog Storage Device Using EEPROM Technology”, by Trevor Blyth et al., ISSCC91/Session 11/Emerging Circuit Technologies/Paper TP 11.7, 1991, page 192.
Applications of an analog storage device have evolved from simple telephone message recordings to the recent development of compensation for the temperature characteristics of laser diodes in CD-ROM burners and high-speed optical communication systems. The latter segments of technologies often require the design of a circuit that compensates for temperature variations. For example, the bias currents and modulation currents required to maintain constant output levels from a laser diode in an optical transmitter vary with temperature.
Accordingly, it is desirable to design a system that employs a programmable analog transfer function capability for compensating variations, such as temperature fluctuations, in the system.